Where do I even begin. Like the title says, my mom is 100% convinced that a person she dated and rejected a few years ago has been controlling her life through people in her close proximity, mainly her (former) friends, close ones (me, my sister, her mother, ...) and our neighbors.

First let me describe this person that I have pieced together through a lot of talking and listening the past 5 years. He is a man she dated 5 years ago and rejected, which in turn lead him to do all these things to her, because "he never in his life got denied anything and I rejected him, so he is trying to make my life miserable". He's a Jew (plays a major role in her story) that works for some kind of detective agency which has the sole purpose of making her life miserable. He's extremely well spoken and is a world class hacker, seeing that he can convince literally anyone to do anything to scare her/ make her miserable in some way and can access any information on anyone. Some examples: every electronic device she owns is bugged in some magical way. Laptop? keylogged after every reinstall of the OS. All the phones she had over the years? All bugged. Our router is hacked and send everything she does to him. He can listen to all conversations she has on Skype and by mobile and can read all the text messages she sends and receives.

Like I mentioned he is also a true master of human psychology, seeing that he can without failure convince literally ANYONE to do ANYTHING. Convince her mother, my grandmother, to say things to her? No problem. Convince the mobile service provider to give him access to every activity on her phone? Check. Convincing a bank to give them all her bank details? Done that. Convince every person of a certain descent to say things to her that would in a very specialized way remind her of him? Done that to at least 20 people I know of. He does this by either searching for deep, dark secrets in the lives of people that would convince them to fulfill every command he gives them, seeing that otherwise he would "spread these secrets to the right people to ruin their lives". As I mentioned, I myself can name at least 20-30 people that she thinks are fulfilling or have fulfilled his commands, and pointing out that there is literally no person on this planet with the power to hack into the lives of at least 30 people around the globe, unveil their darkest secrets, make them shut up about the fact that this person literally invaded their whole personal life to find dirt on them, and to make them perform some stupid thing like "mentioning that there is a really nice Jewish district in the town she was born" or to make someone of her friends give her a kid's bible, only to find that there is a dried leaf in there that "she picked up on a date with him, which he kept and put in that book just to years later give it to her to remind her of him". She multiple times has claimed that he can write messages using accounts of other people because she can "recognize his writing style anywhere". She dated a person a year or 2 ago, but this was set up from the beginning to gain even more control of her. I can go on and on about different scenario's where she is convinced that her life is being controlled, heck even when our water boiler broke down, the guys that came to fix it were hired to install bugs, camera's or something of that sort in our home...

How do I deal with this? Tomorrow morning we are going to a psychologist to discuss this issue, but she doesn't want to talk to her when I am around because I would interrupt her. I for one am afraid that she will say that everything is fine and dandy, fearing that the psychologist will eventually be part of the system. Even if I talk to the professional myself, she will not be able to discuss the things that she discussed with her and I'm afraid that if any doubt or speck of mistrust forms between her and the psychologist, that seeking professional help will be off the table... She already announced that "this is probably all part of his master plan to put me in a psyche ward or to dismiss any claim that I will have against him when I will go to the police with all the evidence that I have collected on the ground that I am mentally ill" (She has 0 evidence to speak of or to show for, while I showed her years ago how to screenshot something)
What makes me the most afraid is that during one of these extremely ridiculous stories I once said that I absolutely do not believe her. This lead to her having an extreme mental episode where she was declaring that one of these days she was going to disappear and never come back or she will simply slit her throat ... not something that a son wants to hear from his mother. This lead to me having a mental breakdown, were I couldn't keep myself from bursting into tears the following days when I even thought back to those word.

How do I proceed in this situation? Every logical argument in the book has allready been used, but to no avail. Continuing like this is no option, because I am extremely afraid that something one day is going to send her over the edge to do the unthinkable.

tldr; My mother has a really severe case of paranoia and has already multiple times considered and even threatened to coming suicide. What are the best steps I can undertake in this situation and has someone experienced something even remotely similar to her situation?